A constant in Proteus is declared literally and can be used as any other variable, with the limitation that its value cannot be changed.

To declare a constant two methods can be used:

CONST id [=] "string" | number

assigns the specified string or number to id; the symbol '=' is optional, but it is strongly suggested to retain it

TEXT id [=] "string" | number
[text..]
[..]string

assigns the text that follows the method to id; the last line of the text must end with string or number, followed by any number of spaces and tabs; the text is assigned verbatim (no translation of C-like constants) and retains line terminators (CR, CR+LF, LF); this declaration is useful if there are many lines to write verbatim (e.g. HTML headers), to avoid multiple instructions and C-like constants

These methods are not an instruction; at compile time, the constant is created in memory and is assigned the specified value, which cannot be another variable/constant or a calculated expression.

All constants have the following restrictions:

• they cannot be passed by implicit reference;
• if passed by implicit reference, their value is not changed;
• they cannot be redefined during execution and cannot be changed by SET, PSET, ISET;
• they cannot be assigned in a FOR loop.

All constants, like variables, can be local (if declared in a UDF) or public; the function PUB or the prefix '_' can be used to access public constants from a UDF. It is not possible to declare a public constant inside a UDF (this would have no meaning anyway, because assignment is done at compile time, not run-time). The interpretation of a constant follows the rules given for variables.